The speed of light is approximately 186,000 miles per secpnmd or exactly 299 792 458 metres per second. I don't know what you mean by 'compared to 'what', the speed of light is the same in all inertial frames.

The speed of light is approximately 186,000 miles per secpnmd or exactly 299 792 458 metres per second. I don't know what you mean by 'compared to 'what', the speed of light is the same in all inertial frames.

So whatever inertial frame one is measuring by, light travels at c as if the inertial frame was still?